‘Component Technology and Design Parameters’
I looked at the history of solid state devices and I found information on a company called Bell Labs who invented the transistor in 1947. This created the first solid state electronic device being made available in the 1960’s. The electronic solid state devices and components such as semiconductors, transistors, diodes, capacitors, resistors and integrated circuits have all replaced the old vacuum tubes, still used by musicians in their guitar amplifiers. The vacuum tubes were the opposite of solid state and the tubes used to breakdown a lot.
The first radio with a solid state circuitry was called a crystal radio it had a piece of wire positioned on a crystal’s surface and it separated out the lower-frequency audio from the higher-frequency transmitted radio carrier wave. This worked because the current could only travel in one direction. this is to do with the crystals design.
Inch-long integrated circuit chip Red light-emitting diode Transistor
They named it solid state because the current has to pass through solid pieces of semi conductor material. This replaced the electricity passing through a heated vacuum tube.
The difference between the vacuum tube and the solid state is a lot to do with the amplitude and the solid state transistor amplifier reflects a larger am0plitude, the vacuum tube warmed up and then passed a signal to a grid and then that created the higher output. But of course electronic technology was restricted because of the fact that the tubes were fragile and could break easily so the solid-state system could be put into areas that would help such as cars, TV’s, planes and military machines.
What the solid-state system uses is a lower DC voltage and with no warm up time. With digital circuits an integrated circuit chip is just a collection of transistors and wires that connect.
This integrated circuit was invented in America by Jack Kilby and Robert Noyce.
There was an argument over who invented the solid state system and it was finally agreed that Kilby would get a share as he proved the system worked and Noyce would get a credit for inventing the planar process method of connecting the circuit’s components. Noyce’s laboratory in California eventually became what we know today as ‘Silicon Valley’. Kilby created the first electronic consumer devices with a transistor hearing aid invented in the 1950’s and in the mid 60’s the first pocket calculator. If it wasn’t for the integrated circuit invention then we wouldn’t have the world of microelectronics. Also quartz watches need the integrated circuit as the oscillation makes the quartz crystal work. When they added a microprocessor it made the watch do more and created a watch like a microcomputer.
Rectifier vacuum tubes were replaced by diodes; these transform AC to DC current. Other replacements have been the incandescent bulbs now replaced by cool running light emitting diodes we call LED’s. You can now find solid state systems in many places such as, thin cameras and disk drives, cell phones, or car dashboard. Voice chips, remote controls, laser pointers, mp3 players, quartz watches. Image sensors in digital cameras, computer monitors and your computer mouse.
The biggest impact we have had on our society is semi conductors. This has led to the micro processor chips in computers being made.
This is the latest technology R8000 microprocessor chip for computers and it replaces the old micro processors by its new chip technology that has an advanced instruction set architecture that allows it to expand its performance this allows it to go faster and process more numbers with technical electronic components.
This is the biggest advancement we have had in our society and the semiconductors are at the centre of everything we use today. Semi conductors now use silicon, and that has started ‘Silicon valley’, now silicon is at the heart of any electronic device or component.
Silicon in the periodic table.
In the silicon lattice all the silicon atoms bond together and this makes a silicon crystal an insulator rather than a conductor.
Metals can conduct electricity because of free electrons that can move between atoms and electricity is the flow of electrons. In silicon the electrons cannot move around, a pure silicon crystal lets very little electricity flow through, this can be changed by something called doping. This means you mix an impurity into the silicon.
The diode is the easiest semiconductor and it allows current to flow one way only. It allows electrons to only pass one way. The P & N Type aren’t conductors alone but the negative electrons get attracted to the positive of the battery and the positive holes in the P-Type get attracted to the negative terminal of the battery.
A transistor is created using three layers, a diode is two layers. These are created as a NPN or a PNP sandwich. A transistor is a switch or an amplifier. The transistor gets its switching by applying current to the centre layer. The silicon chip is a piece of silicon that will hold thousands of transistors, when all the transistors act as switches they produce Boolean gates and then you can create microprocessor chips and this is the basics of all our electronic components and technology today. Nowadays the electronic companies can put tens of millions of transistors onto a single chip, this process is from silicon to the doped silicon to the transistors to the chips and this has made electronic devices and components now so cheap.
The first ever transistor created in 1947.
Major Milestones in Transistor Electronics
from Bell Laboratories Record magazine – January 1975, p.74
1948 – POINT CONTACT TRANSISTOR
1950 – SINGLE-CRYSTAL GERMANIUM
1951 – GROWN JUNCTION TRANSISTOR
1952 – ALLOY JUNCTION TRANSISTOR
1952 – ZONE MELTING AND REFINING
1952 – SINGLE-CRYSTAL SILICON
1955 – DIFFUSED -BASE TRANSISTORS
1957 – OXIDE MASKING
1960 – PLANAR TRANSISTOR
1960 – MOS TRANSISTOR
1960 – EPITAXIAL TRANSISTOR
1961 – INTEGRATED CIRCUITS
A transistor made by Western Electric in 1954
A top hat style transistor from the 1960’s
Silicon crystals are grown for device production and are produced by the Czochralski process. This is shown as (CZ-Si) it is also the cheapest way to do this.
Some impurities from the process happen because the crucible that contains the melt dissolves. For high powered electronic applications the Czochralski method is not pure enough so they have to use float zone silicon production this is shown as (FZ-Si)
A puller rod with seed crystal for growing single-crystal silicon by the Czochralski process
Wafers are made of highly pure and defect free single crystalline material. The process for forming crystalline wafers is known as Czochralski growth. In this process, a cylindrical ingot of high purity crystalline silicon is formed by pulling a seed crystal from a ‘melt’. The ingot is then sliced with an inner diameter diamond coated blade and polished to form wafers.
The Czochralski process it is named after the Polish scientist Jan Czochralski, who discovered the method in 1916 while investigating the crystallization rates of metals.
A silicon wafer
2 inch, 4 inch, 6 inch, and 8 inch wafers
Wafers are grown from crystals that have a regular structure, silicon has a diamond structure.
One unit cell of the diamond cubic crystal structure
This diamond cubic crystal structure is important for electronics. They display an octahedral cleavage that is that they have four planes and directions that follow the faces of the octahedron so that they are stronger. Chemical etching can be used to produce pyramidal structures that are used in Microelectromechanical systems.
Capacitors are used in electronic components to store energy when it has been disconnected from the energy. It is the battery type of the component. Most electronic devices have capacitors and they help store memory settings.
Various types of capacitors. From left: multilayer ceramic, ceramic disc, multilayer polyester film, tubular ceramic, polystyrene, metallized polyester film, aluminium electrolytic.
Various capacitors. The large cylinders are high value electrolytic types
Different capacitors are used in different devices depending on what the device is used for. Metal and copper electrodes that are separated by a vacuum with an insulating glass or ceramic are used in radio transmitters and other higher voltage devices these are of a low capacity type. They use vacuum variable capacitors because they have a maximum capacitance rate up to 100 this lets any tuned electronic device to cover a full frequency. The vacuum system is the best way of stopping the zero loss tangent and is the perfect dielectric. This gives a very high power to the transmitter with no loss and no heating up. Depending on the design of the application a different capacitor is used each time. This is called sensing, some capacitors can sense or measure humidity in the air. Other capacitors can measure the fuel levels in a plane. Other capacitors with flexible plates can look at the strain and pressure on materials, maybe on a planes airframe. Or for maybe space shuttles and stations. Other capacitors are found in microphones as one plate is moved by the air pressure towards the fixed plate.
An accelerometer designed at Sandia National Laboratory.
Accelerometers measure acceleration and also gravity induced reaction force. They sense vibration and shock and used a lot in portable electronic devices. MEMS (Micro electro-mechanical systems) capacitors are put onto chips that are used in lots of electronic products such as smart phones, pda’s, iphones and the Nokia N95, these are used for interface control between modes in the applications.
Apple has had them fitted to their computers since 2005 and protects the hard disk. Also the new Wii has them installed. A lot are used to detect vibration in cars and buildings also in airbags in cars. They are used so much nowadays that they cost very little to use. Other machines that use them are a musical instrument called a Theremin and fingerprint sensors. The military use special low inductance and high voltage capacitors for pulsed power applications like lasers, pulse forming networks, radar and for particle accelerators. Other uses are for exploding bridgwire detonators, and nuclear weapons. Now the military are using banks of capacitors as power for electro magnetic armour and electro magnetic rail guns or coil guns. Capacitors can be dangerous and can explode if they are not properly shielded; they also emit an x-ray that has to be protected from. There are air capacitors that work with an air gap and you can make your own radio.
A home made air capacitor
In timer circuits they use a plastic film so that the metal has a deposit on the plastic and is a metalized film. These are made stable and used for timer circuits. They are able to use higher frequencies.
A film type capacitor that is used in a micro water pump for a washing machine.
Mica capacitors perform extremely well in high
quality audio equipment giving excellent sonic qualities
because of their unique manufacture and use of non magnetic materials in their construction.
IC Card with a Mica capacitor.
The IC card is part of a data carrier system and it is a reader/writer device that induces a voltage in an antenna coil and a capacitor, this is what they call a contactless IC card and is used to send an receive signals. In the diagram are the basic PCB elements of an IC chip a resonance circuit that has an antenna coil and a capacitor. These new PCB’s are laminated with a polyimide film and a copper foil and are cheaper to produce than than the old copper layered cards. The problem is that the frequency of the IC card becomes unstable due to the adhesive changing the dielectric constant the polymide film doesn’t help either. It is now up to the companies to invent the IC card that will have a stable resonance that can still be made cheap. Some inventors have now found that using a mica film stabilizes the IC card because the water absorbed by the mica film is very low. They also used an anisotropic conductive adhesive that helps.
The paper capacitor is made of metal foil and separated by waxed paper. This is the dielectric material. You cannot put more than 600 volts through this capacitor. They are usually sealed with wax. They can fail after a long time.
Ceramic capacitors use a ceramic dielectric these are made from thin films of metal that are attached to the ceramic. They have a very high temperature usage and high dissipation; they are used a lot in filtering applications and for applications that need to use high frequencies.
An ELECTROLYTIC CAPACITOR
Electrolytic capacitors are used when you need a lot of capacitance and they have an electrolyte inside of them. It can be a liquid or it can be dry. The dry type has two metal plates and they are separated by the electrolyte. They usually are put in a round case and this acts as a negative terminal. They can be poor when used in heat and can be unstable. They also are not suitable for high frequency applications.
Glass capacitors are used for expensive applications; they are stable over a wide range of temperatures. Glass capacitors are used in the design of a lot of military applications such as:
Radiation Hardened Circuitry
Burn in Oven Circuitry +200°C
High Temperature Circuitry
R.F. Amplifiers Output Filters
Low Noise Receiver Front Ends
Variable Frequency Oscillators
Voltage Controlled Oscillators
Sample and Hold Capacitor
Low Temperature Circuitry
Bridge Reference Capacitors
Temperature Sensing Circuitry
Jet Engine Monitors
Porcelain Capacitor Replacements
Medical Monitoring Circuitry
Missile Systems and Avionic
These capacitors are made from carbon aerogel and carbon nanotubes. They have an extreme high capacity and can be used instead of recharging batteries. They are used commercially for energy smoothing and can be found in tanks and subermarines for their motor start-ups. They can now be found on diesel trucks and trains. They are now used in some cars for braking as they react quicker than batteries. They could also be used in the future as an alternative for the batteries in electric cars of the future as they are quick charging, stable in temperatures and have excellent safety.
These capacitors are used to work on mains voltage power circuits and can handle large currents they also have a high DC breakdown voltage. This type of capacitors are widely used in ac motor start and run at 50HZ/60HZ, Use well in water pump, air compressor, washing machines.
Capacitors are the main component in most electronic hardware today and depending on the use of the application or machine then it all depends on what capacitor is used for the job. This also changes the fabrication and design of the product as the capacitors and their location have to be taken into account. The IC card had to be re-designed to the change because of what the capacitor needed to achieve. In all cases the invention of the capacitor decides the design of the product and its application as without the special capacitor for the job then the machine or application cannot work.
A 1983 spectrum computer board
PCB Layout Program
The design of the PCB (Printed circuit board) can then be made once you decide what components you need and the job it needs to do. PCB’s can then support any of the electrical applications on the inventions. The PCB’s use conductive pathways to achieve this. Usually they are traced or etched from copper sheets then laminated onto non conductive substrate. They are also called PWB’s or etched wiring boards. With all the other components on the board they are called a PWA (Printed circuit assembly) or else a PCBA (printed circuit board assembly) The PCB’s are usually very good and reliable as well as being strong. They do need a lot of work in the beginning and can cost because of this. They can be wire wrapped or else of a point to point construction. For high volume making they are of course a lot cheaper. The PCB’s have to follow ICP guidelines.
They are made by etching onto the board. So a blank PCB is made the unwantened copper is removed after putting on a mask. This then leaves the coppertraces. Some are made by adding traces to the bare boards. This is called electroplating. Electroplating uses electric current to reduce some of the material on the board and to also coat the board with thin layers of metal. The three methods used for removing copper are, silk screen printing, photoengraving and PCB milling.
Silk screen printing allows writing to be made in the PCB. Photoengraving uses a photo mask and chemicals to etch copperfoil from the substrate; this is done with a photoplotter. The PCB milling uses a two to three axis milling system to mill away the copper foil from the substrate; this then can extract files from PCB design software and add then to the board. The holes on the boards are drilled using tungsten carbide bits.
In the old days they plated the copper with solder but now it has changed to reduce the lead due to EU controls. They also use OSP (organic surface protectant) and IAG (Immerson silver), immersion tin, electroless nickel and immersion gold, also direct gold. Some connectors on the edges of the boards are gold plated.
To test the boards they do a bare board test so that they test each circuit connection as shown on their netlist. In high production they use a bed of nails tester or a fixture as well as a rigid needle adapter this connects to the copper holes to aid in testing. They use a computer to do the test and it sends electric through each contact point. For other boards they use a flying probe or flying grid tester that uses moving heads to contact with the holes.
Then the components can be added this is called a printed circuit assembly (PCA).
There are two ways to do this either through hole construction or surface mount construction. The component leads are electrically and mechanically put onto the baord with molten metal solder. The board when ready made is tested again using a visual test and automated optical inspection, this is to check quality control and they have to follow strict JEDEC guidelines for everything. Other tests are analogue signature analysis and power off testing. With the power on they do an in circuit test to measure voltage and a functional test so that the PCB does what it is designed to do. They also put on extra pads to do these tests. If the board fails the tester may desolder and replace the components.